> You probably safely assume that you can replace table salt with kosher salt, or table salt with coarse rock salt (provided it will dissolve in cooking). However, you hopefully know that if the recipe calls for kosher salt you may not be able to use iodised table salt instead (if doing a fermentation), and that table salt is not a happy substitute for coarse salt for finishing.

Hopefully he'd also know that 99% of recipes that use kosher salt (presumably because it sounds fancier) will work just fine with with table salt (iodised or not). For most uses the grain size will not make any difference at all and for the remaining ones it is still not essential.